The present invention is directed to a suspended ceiling structure formed by main runners and cross runners which have an inverted T configuration with a web with two flanges extending from the base of the web to form rectangular openings which receive panels and each of the runner members is provided with centering bumps to help maintain the panels in a desired position to have maximum support thereof.
In ceiling constructions, it has always been desirable to maintain a position of the panel relative to the runner members. In Snaith, U.S. Pat. No. 3,359,696, the panels were provided with grooves and it was desired to maintain the panels relative to the flanges so that the aesthetic appearance would be maintained. In order to do this, the patentee suggests using clips which were inserted on the webs of the T members or by providing bumps such as dimples that were formed in the web and extended on opposite sides.
A concern with maintaining the position of the panels becomes more critical when utilizing runners having narrow flanges such as in the order of a total width of 1/2 inch to 5/8 inch so that each of the flanges has a width which is roughly less than 5/16 of an inch. With such a narrow runner, it is conceivable that the panel can be shifted into one corner in the rectangular opening so that it is not properly supported in the opposite edges or sides. This becomes particularly critical when maintaining fire reading of the panel or ceiling system. One proposal of aiding in positioning the panels to ensure proper support comprises a pair of right angle cuts with one leg of each cut extending parallel to the flange and the other being substantially vertical thereto. The material between these pair of cuts is then deformed out to form two bumps for centering purposes. Such an arrangement has been sold as the Centricitee .TM. Grid System. One disadvantage of this type of centering projection or bump is that the sharp edge along one side of the bent out portion may dig into the panel and prevent adjustment of the panel in the rectangular opening.
Another problem with using dimples, which was suggested by the above mentioned Snaith patent, is that the provision of the dimple when close to the flange may cause drawing or pulling of metal from the flange which would destroy its aesthetic appeal.